The present invention relates to apparatus for preparing the ends of pipe sections that are to be welded together end-to-end; and more particularly, it relates to an improvement in apparatus for forming precision machined surfaces on the ends of large diameter pipeline sections such that the apparatus cleans the exterior of the pipe simultaneously with the machining of the end.
Pipelines for transporting crude oil and the like are formed by welding pipe sections together to form a pipe string which is buried underground or laid underwater from a lay barge. Generally, such pipelines will be comprised of pipe having a diameter of 30 inches O.D. or even larger. Preparatory to the welding of pipe sections together to form a pipe string, the end of each of the sections must be prepared for welding. Especially for automatic girth joint welding, a high precision is needed in end preparation operations. Preparation of the pipe ends prior to welding involves forming the joint in a true plane, that is one which is perpendicular or substantially perpendicular to the axis of the pipe. Preparation also involves cutting or machining of the pipe ends to provide a bevelled end such that the abutting ends to be welded together will provide a V-groove.
Apparatus for forming precision surfaces on the ends of large pipes include a rotating, tool-carrying face plate mounted on an axis that is firmly supported on an internal pipe clamp. Illustrative of pipe facing machines which cut pipe ends of various bevel configurations prior to welding is that disclosed in U.S. Pat. No. 3,733,939. The apparatus disclosed therein comprises a cage shaped double ended aligning clamp which axially aligns and firmly supports a rotatable face plate that carries multiple cutting tools mounted on spring-biased pivoted arms to permit radially inward and outward movement of the tools with respect to the pipe end. The face plate is hydraulically driven around the axis of the clamp to perform the machining operation.
Pipe sections which are to be positioned underwater on or under the ocean floor are usually precoated with a waterproofing and weighting material. These pipe sections are then joined together on the deck of a floating vessel or barge by butt welding into a continuous pipe string. The welded ends of the pipe string are then field-coated with a corrosion resistant material, and the resulting pipe string is subsequently launched from the stern of a lay barge to the ocean floor.
Accordingly, prior to welding of the pipe ends together, it is necessary to clean the ends of the pipe sections to provide a clean welding surface. It is both time consuming and troublesome to clean the pipe end in a separate operation; and particularly, since time is of the essence in an off-shore pipe laying situation, it would be desirable to reduce the time necessary for preparing and of cleaning pipe ends prior to welding.
Numerous machines have been developed for cleaning the outside surface of large-diameter pipe. Most of these are self-propelled units having brushes pulled into contact with the exterior surface of the pipe and moved relative thereto to buff the pipe. Most, if not all, of the self-propelled traveling pipe cleaning machines were developed for and are utilized in pipeline welding situations wherein the pipeline is to be laid underground. Accordingly, the pipe cleaning machines are for cleaning the entire exterior surface of a pipe prior to the pipe being primed with a protective corrosion proof coating and laid in a trench. The cleaning machines, therefore, will typically include a large boom having large internal combustion engines mounted thereon to power the pipe cleaning machine. Illustrative of prior art pipe cleaning machines are those disclosed in U.S. Pat. Nos. 3,495,288; 3,916,469; 2,064,577 and 1,815,573. All of these systems relate to an apparatus for cleaning and removing rust, scale and other corrosion or foreign matter adhering to the outside of pipes, so that a protective coating may be thereafter applied over the entire exterior surface of the pipe.
Accordingly, there is a need for apparatus particularly suited for use in offshore pipe laying situations for not only machining the annular ends of large diameter pipe in the field in preparation for welding, but also effecting the simultaneous cleaning of the pipe ends to remove excess coating, corrosion or foreign matter therefrom.